duanbeng8872 2016-02-20 08:23
浏览 289


I want to send bulk mail from a server application written in golang. I just don't want to use any third-party smtp server to avoid usage quota limitations.

How can I send email without a smtp server? Is smtp package in standard library can help me? All example I see using the smtp package requires a third-party smtp server to send email.

  • 写回答

2条回答 默认 最新

  • doudouji2016 2016-02-20 10:20

    There is only one way to send an e-mail message without directly communicating with an SMTP server: delegate this action to some other program.

    What program to pick, is an open and wide question in itself because there are lots of programs which are able to send mails.

    On the other hand, if we talk about POSIX systems such as GNU/Linux- or *BSD-based operating systems, they usually come with the binary /usr/sbin/sendmail or, sometimes, /usr/bin/sendmail which is either provided by the real Sendmail package or by another MTA which exist in abundance—ranging from full-blown MTAs such as Postfix or Exim to narrow-scoped "null-clients" such as ssmtp or nullmailer.

    This program is usually called with the -t command-line option which makes it read the addresses of the message recipients from the To headers of the mail message itself.

    Basically calling /usr/sbin/sendmail -t and piping the full message's text to its standard input is what PHP's mail() function does, FWIW.

    While you can do this call directly using the os/exec, net/mail and net/textproto standard packages, the popular gomail package provides a simpler way to do that: its Message type provides the WriteTo() method which is able to write to a running Sendmail instance, like this (copied from a real program of mine):

    const sendmail = "/usr/sbin/sendmail"
    func submitMail(m *gomail.Message) (err error) {
        cmd := exec.Command(sendmail, "-t")
        cmd.Stdout = os.Stdout
        cmd.Stderr = os.Stderr
        pw, err := cmd.StdinPipe()
        if err != nil {
        err = cmd.Start()
        if err != nil {
        var errs [3]error
        _, errs[0] = m.WriteTo(pw)
        errs[1] = pw.Close()
        errs[2] = cmd.Wait()
        for _, err = range errs {
            if err != nil {

    Actually, relying on MTA to deliver your mails has an advantage is that full-blown MTAs support mail queuing: that is, if an MTA is unable to send your message right away (say, due to a network outage etc) so it will save the message in a special directory and will then periodically try delivering it again and again until that succeeds or a (usually huge, like 4-5 days) timeout expires.

    本回答被题主选为最佳回答 , 对您是否有帮助呢?



  • ¥15 UltraScale 系列 Bitslip 技术支持
  • ¥15 一个线程在sleep的时候set一个信号会起作用吗
  • ¥100 需求高精度PT100设计电路和算法
  • ¥15 单片机配网,继电器开关,广播
  • ¥60 Qcustomplot绘制实时动态曲线
  • ¥20 运用matlab画x-y图
  • ¥15 用idea运行项目,运行tomcat报错:断言失败
  • ¥15 Sqlserver查询链接服务器数据问题
  • ¥15 Bibtex4Word 引用中文文献
  • ¥20 用opencv c/c++ 转换成灰度图,然后做一下直方图均衡,输出mp4文件